While hippos are known for their speed both on land and in water, they would face insurmountable difficulties during a the biking portion.

Hippos have short, stout legs relative to their bulky body size. Even if we entertain the hypothetical scenario of a hippo magically being able to ride a bike, these short legs would severely restrict their pedaling efficiency.

Their weight, coupled with the slow biking speed resulting from their short legs, would most likely cause any lead from the swimming and running stages to dissipate rapidly.

Additionally, despite their intimidating size and strong jaws, hippos are not carnivorous by nature, but rather herbivores with a diet primarily composed of grasses. While they can be aggressive if they perceive a threat, they don't typically target humans as food. Therefore, the scenario of a hippo eating a competitor during a the other stages is extremely improbable.

All things considered, a relatively fit human athlete would still have a considerable edge in a triathlon competition against a hippo.